JPS60124436A - Production of molding sand composition for cold box - Google Patents

Abstract

PURPOSE:To increase the degree of bonding of molding sand for a cold box by mixing refractory particles of silica sand, etc. and a silane coupling agent at a specific weight ratio then adding a binder consisting of a resin, etc. thereto and kneading the mixture. CONSTITUTION:A silane coupling agent is compounded and mixed at 0.001- 0.1pt.wt. with 100pts.wt. refractory particles such as silica sand or the like to bond satisfactorily the silane coupling agent to the surface of the refractory particles. A binder consisting of a resin etc. is added thereto and the mixture is kneaded to make the mol.wt. of the silane coupling agent and the resin increasingly higher in mol.wt. The molding sand for a cold box manufactured in the above-mentioned way is made into the good molding sand having high bonding strength.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a method for producing a foundry sand composition for a cold box.

(Prior Art) Conventionally, a foundry sand composition formed by coating refractory particles such as silica sand with a resin has been used for molding molds, cores, and the like. Hot box methods such as the shell molding method are conventionally known methods for producing molded objects such as molds and cores using this foundry sand composition, and are capable of producing hard and durable objects. For this reason, this hot box method is the mainstream. However, since this pot box method is a method of manufacturing molded objects such as molds and cores by heating and curing the foundry sand composition, it requires fuel for heating and also requires the use of molding sand compositions. There is a problem with pollution, such as the generation of foul-smelling gas when curing by heating. Therefore, in recent years, attempts have been made to reduce the amount of binder such as resin that coats refractory particles in order to improve the pollution problem without sacrificing the bonding strength of the molded object. Reducing the amount of resin that coats certain 6 refractory particles will reduce the amount of foul-smelling gas generated, which can help alleviate pollution problems, but at the same time, it will also reduce the bonding strength of the molded product. It is predicted that the bonding strength of the molded product will decrease, and as a means of suppressing the decrease in the bonding strength of the molded product, it is disclosed, for example, in JP-A-57-177848, to incorporate a silane coupling agent into the foundry sand composition. ing.

What is disclosed in this Japanese Patent Application Laid-open No. 57-177848 is
When kneading refractory particles such as sand grains and a binder such as a resin, an aqueous solution of a silane coupling agent is simultaneously added to obtain a foundry sand composition. By using the molding sand composition produced in this way, it is possible to improve the pollution problem without sacrificing the bonding strength of the molded product, but the hot box method Since it is a method of obtaining a molded object by heating and hardening the object, it is not desirable from the perspective of saving energy, and there is a limit to the reduction in the amount of foul-smelling gas generated.Therefore, recently, the cold box method has been adopted. It's coming.

In this cold box method, refractory particles such as silica sand are coated with a binder such as a resin that hardens through a chemical reaction with carbon dioxide gas (CO2), tertiary amine gas, etc. to form a foundry sand composition. Moldings such as cores are obtained by curing the foundry sand composition in an atmosphere such as tertiary amine gas, but the bonding strength of the moldings obtained by this method is as follows: The drawback is that the bonding strength of the molded product obtained by the Hola I-box method is smaller and more brittle. Therefore, to overcome this drawback, for example,
As disclosed in Japanese Patent Publication No. 43-15161, a silane coupling agent is mixed with a resin in a predetermined amount, and then refractory particles such as sand, silanker, and a resin containing a pulling agent are mixed. The molding sand composition is kneaded to form a molding sand composition, and the molding sand composition thus obtained is used to manufacture a molded object.In the cold box method, the silane compound is Even if a foundry sand composition obtained by adding a ring agent is used, it has not been possible to sufficiently increase the bonding strength of the molded product.

(Object of the Invention) The present invention has been made in view of the above circumstances, and its purpose is to provide a cold box that can increase as much as possible the bonding strength of a molded object produced by the cold box method. An object of the present invention is to provide a method for producing a foundry sand composition for use in manufacturing.

(Structure of the Invention) The present invention was made based on the fact that changing the order of blending silane coupling agents in a foundry sand composition increases the bonding strength of a molded product obtained by a cold box method. The feature is that silane force/sampling agent is first blended into refractory particles such as silica sand, and after the refractory particles and silane coupling agent are mixed,
A binder such as resin is added.

The method for manufacturing a molding sand composition for a cold box according to the present invention will be explained with reference to the drawings. As shown in FIG. 1, refractory particles 1 and silane coupling agent 2 are mixed in a predetermined ratio. Then, a binder 3 is added to the refractory particles 1 containing a silane coupling agent, and the binder 3 and the refractory particles containing a silane coupling agent are kneaded to form a foundry sand composition 4. This is what I did to get it. By composing the foundry sand composition 4 in this way, it is possible to obtain a large bonding strength when a molded object is manufactured by the cold box method, but this is because the silane coupling agent 2 and the viscous When the resin as the binder 3 is mixed first, polymerization progresses between the silane coupling agent 2 and the resin 3, and the amount of bonding groups between the refractory particles 1 and the silane coupling agent 2 increases. However, according to the present invention, as shown in FIG. 2, the bond between the refractory particles l and the silane coupling agent 2 is first It is considered that more of the silane coupling agent 2 is bonded to the surface of the refractory particles 1, and then the bonding between the resin 3 and the silane coupling agent 2 proceeds. It is understood that when a molded article is manufactured by the cold box method using the manufactured foundry sand composition 4, the bonding strength thereof increases.

The silane coupling agent used in the present invention has the general formula RS
It is expressed as i X x, where the chemical symbol R is a reactive organic group, and the chemical symbol Examples of such groups include a roxypropyl group, an alkylmercapto group, an epoxy group, and examples of hydrolyzable groups include a halogen atom group, an alkoxy group, and an acetoxy group. Among these silane coupling agents, silane coupling agents having an alkylamino group as a reactive organic group and a methoxy group or an ethoxy group as a hydrolyzable group are preferable for producing a foundry sand composition used in the cold box method. , and the amount of the mixture is 100% of the refractory particles.
It is desirable that the range is from 0°001 to 091 parts by weight. That is, the amount of silane coupling agent added is 0 to ioo parts by weight of the refractory particles.
．． If the amount of the silane coupling agent is less than 0.001 parts by weight, it is difficult to expect an improvement in the bonding strength of the molded product formed by the cold box method.
If the amount is more than 0.11 parts by weight per 100 parts by weight of the refractory particles, the viscosity of the refractory particles mixed with the silane coupling agent will increase, and the time available for use as a foundry sand composition will be shortened. Therefore, it is practically difficult to provide it as foundry sand for cold boxes.

It is desirable to mix the refractory particles and the silane coupling agent uniformly, and from the viewpoint of uniformly dispersing the silane coupling agent on the surface of the refractory particles, it is desirable to mix the silane coupling agent and the refractory particles. It is preferable to add the binder at least 10 minutes after mixing.

The above-mentioned points 1 and 2 will become clear from the examples described below.

(Example) (Example 1) First, a foundry sand composition obtained by first blending and mixing a silane force/sampling agent and a binder, and then adding and mixing refractory particles is used. a molded article obtained by using a molding sand composition obtained by simultaneously adding a silane coupling agent, a binder, and refractory particles;
A comparative example of the bonding strength of a molded product obtained using a foundry sand composition obtained by first mixing a silane coupling agent and refractory particles, then adding a binder and kneading.

It is shown in Table-1.

Here, recycled silica sand obtained by regenerating a foundry sand composition is used for the refractory particles, benzine ether type phenol formaldehyde resin is used as the binder, and polymethylene is used as the curing agent. Polyphenyl polyisocyanate was used, and CH was used as the silane coupling agent.

Structural formula) 12 NC2H4NHC3H6S i (OC
H3) N-β (aminoethyl) r − expressed as 2
Aminopropylmethyldimethoxysilane was used, and the blending ratio of the resin and curing agent was 1.1 parts by weight (1.1%) for 100 parts by weight of recycled sand, and the silane coupling agent was mixed with the recycled sand. It is blended at a ratio of 0.001 part by weight to 100 parts by weight, and the bonding strength of the molded product is determined by the cold box method (hardening the foundry sand composition using amine gas).
The evaluation was made based on the compressive strength of the molded product immediately after molding.

Table 1 From Table 1, compression of molded objects made using a foundry sand composition obtained by first mixing a silane coupling agent and recycled silica sand, and then adding and mixing a resin. The strength is
It is clear at a glance that the compressive strength of molded products produced using foundry sand compositions obtained using other mixing orders is significantly higher.

(Example 2) Next, the type and blending amount of the silane coupling agent were changed, and the compressive strength of the molded product was measured.

In this example, N-B
(aminoethyl) r-aminopropylmethyldimethoxysilane (hereinafter referred to as symbol Y), N-β (aminoethyl)aminepropylmethyldimethoxysilane (
Hereinafter, it will be expressed as symbol Y2. ), Nippon Unicar A-1
100 (r-aminopropylpolymethoxysilane Structural formula H2NCH2CH2C) (2S i (OC2,H
5) Using s (hereinafter expressed as symbol Y3)),
The mixing ratio of the silane coupling agent to 100 parts by weight of silicic acid was 0.005 parts by weight, 0.011 parts by weight, and 0.02 parts by weight.
We decided to change the measurement to three parts by weight. In addition,
In this example, a silane coupling agent and silica sand were blended and mixed for 2 minutes using a kneader, and 15 minutes after mixing, the resin and curing agent described in Example 1 were added.
A foundry sand composition was prepared by mixing the mixture in the proportions described in 2. and kneading it for 2 minutes using a kneader, and the foundry sand composition thus obtained was combined by a cold box method, and the diameter was A cylindrical test piece having a length of about 29 mm and a length of about 50 mm was prepared, and the compressive strength of the cylindrical test piece immediately after molding was measured.

Table 2 From this example, as a silane coupling agent, Y
It is understood that those to which + and Y 2 are added, that is, those in which the reactive organic group is an alkylamino group and the hydrolyzable group is a methoxy group, are preferable.

(Example 3) Next, the compressive strength of the molded article immediately after molding was measured by changing the mixing time of the silane coupling agent and silica sand.

Here, 3.0 kg of silica sand was put into a kneading machine, and N-β(
Add 0.3 g of r-aminopropylmethylmethoxysilane (aminoethyl), change the mixing time to 6 stages, mix, and after 15 minutes, add 30 g each of the resin and curing agent used in Example 1. Using the molding sand composition obtained in this way, a test piece similar to that in Example 2 was prepared, and the compressive strength of the molded product was evaluated. It was measured. The results are shown in Table-3.

Table 3 As is clear from Table 3, in order to increase the bonding strength, it is desirable to mix the silane coupling agent and silica sand for at least 1 minute. This is thought to be because the silane coupling agent is uniformly dispersed on the surface of the silica sand if the silane coupling agent is also mixed with a kneader.

(Example 4) Next, after mixing the silane camping agent and silica sand, the time during which the resin and curing agent were added was changed as appropriate, and the compressive strength of the molded object was measured immediately after molding. .

Here, silane coupling agent 0 is added to 3.0 kg of silica sand.
, 3'g were added, and after mixing these for 2 minutes, six stages of standing were performed to create a test piece similar to Example 2,
The compressive strength of the molded article was measured immediately after molding. The results are shown in Table-4.

Table 4 From Table 4, it has been found that it is preferable to add 10 liters of 10 liters of water before adding the binder in order to increase the bonding strength. This is thought to be because it takes time for the hydrolyzed group of the silane coupling agent to hydrolyze and form a siloxane bond with the silanol group on the surface of the silica sand.

(Example 5) Next, the type of refractory particles was changed, and the amount of silane coupling agent added to the refractory particles was changed, and the bonding strength of the molded product was measured.

Here, the types of refractory particles shown in Table 5 are used, and the amount of coupling agent to silica sand is as follows:
The foundry sand composition was changed by changing the ratio of 0 parts by weight, 0.005 parts by weight, 0.01 parts by weight, 0.02 parts by weight, 0.03 parts by weight, and 0.04 parts by weight with respect to 100 parts by weight of silica sand. manufactured something. The method for preparing the test piece was the same as in Example 2, and the method for mixing the refractory particles and the silane coupling agent was also the same as in Example 2.

Table 5 From Table 5, it is understood that there are differences in the bonding strength of the molded object depending on the type of silica sand, and that the bonding strength changes depending on the amount of silane coupling agent blended with the silica sand. According to this Table-5, the blending ratio of the silane coupling agent is 0.005 parts by weight with respect to 100 parts by weight of the refractory particles.
It can be seen that it is most desirable to set the content to 0.01 parts by weight.

(Example 6) Here, we decided to measure the bonding strength of the molded object against moisture absorption deterioration.

Here, in the case where the coupling agent is added, 1 part by weight of the coupling agent is mixed with 100 parts by weight of silica sand.
．． 0% compounded and without the addition of a coupling agent, 2.
2% was added, and a foundry sand composition was manufactured in the same manner as in Example 2, and a test piece thereof was also prepared in the same manner as in Example 2. The results are shown in Table-6.

As is clear from Table 6, it can be seen that the molded articles manufactured using the foundry sand composition containing the silane coupling agent suffer less deterioration due to moisture absorption.

(Effect of the invention) The present invention secures the bond between the refractory particles and the silane coupling agent by first blending the silane coupling agent with refractory particles such as silica sand, and then caking. Since the sand composition is kneaded with the addition of a silane coupling agent, it is possible to increase the bonding strength between the refractory particles, the silane coupling agent, and the binder. The bonding strength of the molded object formed by the cold box method can be greater than that of the conventional method.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a method for manufacturing a molding sand composition for a cold box according to the present invention, and FIG. 2 is a configuration diagram showing general use of the molding sand composition for a cold box according to the present invention. 1.. Refractory particles 211.. Silane coupling agent 3.. Binder 4.. Foundry sand composition

Claims (1)

[Claims] (1) Cold box molding sand composition characterized in that molding sand for cold boxes is produced by mixing refractory particles such as silica sand with a silane force/sampling agent and then adding a binder such as a resin. How things are manufactured. (2. In claim 1, the silane coupling agent is added in an amount of 0.00% to 100 parts by weight of the refractory particles.
A method for producing a foundry sand composition for a cold box, characterized in that the composition is blended in a proportion of 0.001 part by weight to 0.1 part by weight.